1. Field of the Invention
The present invention relates to a zoom lens and an imaging apparatus, and particularly to a zoom lens having a F number of around 2.8 in brightness, a zoom ratio of around 3 times, and a shorter overall length when retracted and being suitable for a digital still camera, a video camera and the like, and imaging apparatus using such zoom lens.
2. Description of the Related Art
In recent years, a video camera and a digital still camera using a solid state image sensing device have been widely spread rapidly, and high resolution and further miniaturization of those apparatus have been particularly demanded. A zoom lens which has zoom lens construction of negative, positive, and positive types from an object side, and a first lens group having a small number of lenses such as two pieces of concave and convex lenses is disclosed in the patent document 1 and the patent document 2 as a conventional technology.
Patent document 1: Japanese Patent Laid-Open No. 2001-296475
Patent document 2: Japanese Patent Laid-Open No. 2002-372667
However, it is very difficult to obtain a zoom lens for 5000000 pixel-class by applying such conventional technology, because miniaturization of lens is difficult, and further, it is difficult to satisfy a demand for high resolution accompanying with miniaturization of a picture size in an imaging device. Further by chasing miniaturization and high resolution of lens, an influence to a focusing performance by decentering between lenses of the second lens group becomes large, and it becomes difficult to accomplish an improvement in reliability.